Add Lean4 Theorem prover syntax

[universemaster]

A table based format for commands sorted by purpose seems a good fit for Lean 4's theorem prover syntax.

Resources:
https://djvelleman.github.io/HTPIwL/
and
https://leanprover-community.github.io/

[martin12333]

where would you want to insert the column for Lean?

my suggestion:
https://docs.google.com/spreadsheets/d/1Or_sAxcf8G5VGoIXXEJl8Agaz5FOx6qMwwOy9aFH-e4/edit?usp=sharing
(https://docs.google.com/spreadsheets/d/1w4MAxWcWjX3aMBRkOsqjwcAabFtY4WT4JloPRd944og/edit?usp=sharing)

related:
a free book on using Lean 4 as a programming language